Controlling vector mapping using object geometry
Yes, you can do this pretty easily in Cycles using a Mix RGB node.  Since Cycles considers colors and vectors to be no different from each other you can actually run vectors through color sockets and vice-versa.

Just use a Mix RGB node to mix the two vectos with the Backfacing value plugged into the factor.  You can then plug the "Color" output from the Mix node right into the image texture nodes.